1. Field of the Invention
The present invention relates to a recording solution (hereinafter "ink"), and more particularly to an ink suited for systems in which a record is made on a plain paper by ejecting ink, in the form of droplets, from a minute ejection opening (or ejection orifice) provided in a recording head.
2. Related Background Art
Hitherto having been used as inks in writing utensils such as fountain pens and felt pens are those inks comprising various types of dye dissolved in water or other organic solvent.
Inks comprising various types of dye dissolved in water or other organic solvents are also used in ink-jet systems in which recording is performed by ejecting ink from an ejection orifice provided in a recording head, by the action of the oscillation attributable to a piezoelectric oscillator or the electrostatic force attributable to the application of a high voltage. However, the inks for ink-jet systems are required to satisfy more severe conditions with respect to many performances than those required in the writing utensils such as fountain pens and felt pens commonly used.
The ink-jet systems make less noise and can perform high-speed recording or color recording on plain paper without any particular fixing step, and researches have been energetically made on various types.
Various methods are available for the systems of this type, but all of them are required to have the performances such that the physical properties such as viscosity and surface tension are within the range of suitability, the recording agent has a solution satability high enough not to cause clogging of the minute ejection orifice, a recorded image can be obtained in a sufficiently high density, and changes in the values of physical properties, precipitation of solid contents, or the like may not occur during storage.
In addition to the above performances, they are also required to have the properties that the recording can be performed without limitation on the type of recording members, they can achieve a high fixing speed, and they can give a recorded image with excellent water resistance, solvent resistance (resistance to alcohol, in particular), light-resistance, wear resistance, and resolution.
However, recorded images formed using conventional inks, in particular, water-based inks, tend to cause feathering or blur, or color fading, owing to adhesion of water or irradiation by light. This tendency is remarkable particularly in a magenta recording, and inks improved to eliminate these disadvantages have been strongly sought.
For example, Japanese Patent Laid-Open No. 59-78273 discloses an ink comprising a specific monoazo dye having a phenyl group and a naphthyl group.
When a recording is performed on a plain paper by using such an ink, the resulting recorded image can have a light-resistance greatly superior to that of inks comprising a conventional magenta dye, but can not still have a water resistance having reached a level high enough for practical use.